U.S. patent application number 11/218949 was filed with the patent office on 2007-03-08 for catalytically inactive heat generator and improved dehydrogenation process.
This patent application is currently assigned to Sud-Chemie Inc.. Invention is credited to Vladimir Fridman, Jay S. Merriam, Michael A. Urbancic.
Application Number | 20070054801 11/218949 |
Document ID | / |
Family ID | 37651044 |
Filed Date | 2007-03-08 |
United States Patent
Application |
20070054801 |
Kind Code |
A1 |
Fridman; Vladimir ; et
al. |
March 8, 2007 |
Catalytically inactive heat generator and improved dehydrogenation
process
Abstract
An improved dehydrogenation catalyst bed system for olefin
production utilizing classical processing techniques is disclosed.
The catalyst bed system comprises a dehydrogenation catalyst
comprising an active component selected from an oxide of a metal of
Group 4 or Group 5 or Group 6 and combinations thereof and a
support selected from aluminum oxide, aluminas, alumina
monohydrate, alumina trihydrate, alumina-silica, transition
aluminas, alpha-alumina, silica, silicate, aluminates, calcined
hydrotalcites, zeolites and combinations thereof mixed with a first
inert material selected from any material that is catalytically
inactive when subjected to reaction conditions that can effect
dehydrogenation of olefins and that has a high density and high
heat capacity and that is not capable of producing heat during any
stage of the dehydrogenation process, and the dehydrogenation
catalyst plus the first inert material then being physically mixed
with a secondary component comprising a heat-generating inert
material and a carrier capable of supporting the heat-generating
inert material, wherein the secondary component is catalytically
inert with respect to dehydrogenation reactions or to cracking or
to coking and generates heat after being exposed to reducing and/or
to oxidizing reaction conditions.
Inventors: |
Fridman; Vladimir;
(Louisville, KY) ; Merriam; Jay S.; (Louisville,
KY) ; Urbancic; Michael A.; (Louisville, KY) |
Correspondence
Address: |
SUD-CHEMIE INC.
1600 WEST HILL STREET
LOUISVILLE
KY
40210
US
|
Assignee: |
Sud-Chemie Inc.
|
Family ID: |
37651044 |
Appl. No.: |
11/218949 |
Filed: |
September 2, 2005 |
Current U.S.
Class: |
502/318 ;
502/320 |
Current CPC
Class: |
B01J 23/26 20130101;
C07C 2523/889 20130101; C07C 2521/08 20130101; C07C 2529/04
20130101; Y02P 20/584 20151101; Y02P 20/52 20151101; C07C 5/322
20130101; C07C 2521/02 20130101; C07C 2523/72 20130101; B01J
35/0006 20130101; C07C 2521/04 20130101; C07C 2523/02 20130101;
C07C 2523/06 20130101; B01J 23/72 20130101; C07C 2523/26 20130101;
C07C 2523/34 20130101; C07C 2521/12 20130101; C07C 2523/04
20130101; C07C 2521/10 20130101; B01J 23/32 20130101; C07C 5/322
20130101; C07C 11/06 20130101 |
Class at
Publication: |
502/318 ;
502/320 |
International
Class: |
B01J 23/26 20070101
B01J023/26 |
Claims
1. In a catalyst bed system for use in adiabatic non-oxidative
dehydrogenation processes comprising an oxide of chromium on
alumina dehydrogenation catalyst mixed with a granular,
alpha-alumina material having a similar particle size to said
catalyst, the improvement comprising physically mixing said
dehydrogenation catalyst plus said alpha-alumina material with a
secondary component comprising a heat-generating inert material
selected from the group consisting of copper, manganese and
combinations thereof, and a carrier capable of supporting the
heat-generating inert material, wherein said secondary component is
catalytically inert with respect to dehydrogenation reactions or to
cracking or to coking and generates heat after being exposed to
reducing and/or to oxidizing reaction conditions.
2. The catalyst bed system of claim 1 wherein said secondary
component carrier is selected from aluminum oxide, aluminas,
alumina monohydrate, boehmite, pseudo-boehmite, alumina trihydrate,
gibbsite, bayerite, alumina-silica, transition aluminas,
alpha-alumina, silica, silicate, aluminates, calcined
hydrotalcites, zeolites, zinc oxide, chromium oxides, magnesium
oxides and combinations thereof.
3. The catalyst bed system of claim 1 wherein said heat-generating
inert material comprises from about 1 wt % to about 40 wt % of the
total secondary component weight.
4. The catalyst bed system of claim 3 wherein said heat-generating
inert material comprises from about 4 wt % to about 20 wt % of the
total secondary component weight.
5. The catalyst bed system of claim 4 wherein said heat-generating
inert material comprises from about 6 wt % to about 10 wt % of the
total secondary component weight.
6. The catalyst bed system of claim 1 wherein said secondary
component further comprises a promoter selected from an alkali, an
alkaline earth metal, lithium, sodium, potassium, rubidium, cesium,
beryllium, magnesium, calcium, strontium, barium and a combination
thereof.
7. In a catalyst bed system for use in adiabatic non-oxidative
dehydrogenation processes comprising a dehydrogenation catalyst
comprising an active component selected from an oxide of a metal of
Group 4 or Group 5 or Group 6 and combinations thereof and a
support selected from aluminum oxide, aluminas, alumina
monohydrate, alumina trihydrate, alumina-silica, transition
aluminas, alpha-alumina, silica, silicate, aluminates, calcined
hydrotalcites, zeolites and combinations thereof mixed with a first
inert material selected from any material that is catalytically
inactive when subjected to reaction conditions that can effect
dehydrogenation of olefins and that has a high density and high
heat capacity and that is not capable of producing heat during any
stage of the dehydrogenation process, the improvement comprising
physically mixing said dehydrogenation catalyst plus said first
inert material with a secondary component comprising a
heat-generating inert material and a carrier capable of supporting
the heat-generating inert material, wherein said secondary
component is catalytically inert with respect to dehydrogenation
reactions or to cracking or to coking and generates heat after
being exposed to reducing and/or to oxidizing reaction
conditions.
8. The catalyst bed system of claim 7 wherein said dehydrogenation
catalyst comprises an oxide of chromium on alumina.
9. The catalyst bed system of claim 7 wherein said first inert
material is a granular, alpha-alumina material having a similar
particle size to said catalyst.
10. The catalyst bed system of claim 7 wherein said heat-generating
inert naterial is selected from copper, chromium, molybdenum,
vanadium, cerium, yttrium, scandium, tungsten, manganese, iron,
cobalt, nickel, silver, bismuth and combinations thereof.
11. The catalyst bed system of claim 7 wherein said heat-generating
inert material is selected from copper, manganese and a combination
thereof.
12. The catalyst bed system of claim 7 wherein said secondary
component carrier is selected from aluminum oxide, aluminas,
alumina monohydrate, boehmite, pseudo-boehmite, alumina trihydrate,
gibbsite, bayerite, alumina-silica, transition aluminas,
alpha-alumina, silica, silicate, aluminates, calcined
hydrotalcites, zeolites, zinc oxide, chromium oxides, magnesium
oxides and combinations thereof.
13. The catalyst bed system of claim 7 wherein said heat-generating
inert material comprises from about 1 wt % to about 40 wt % of the
total secondary component weight.
14. The catalyst bed system of claim 7 wherein said secondary
component is prepared by precipitation of said secondary component
carrier with said heat-generating inert material.
15. The catalyst bed system of claim 7 wherein said secondary
component is prepared by impregnation of the secondary component
carrier with the heat-generating inert material.
16. The catalyst bed system of claim 7 wherein said secondary
component further comprises a promoter selected from an alkali, an
alkaline earth metal, lithium, sodium, potassium, rubidium, cesium,
beryllium, magnesium, calcium, strontium, barium and a combination
thereof.
17. The catalyst bed system of claim 7 wherein said catalyst and
said first inert material and said secondary component have a
volume relationship defined by the equation: (vol. catalyst)/(vol.
first inert material+vol. secondary component)=0.25 to 0.75. and
wherein said first inert material and said secondary component have
a volume relationship defined by the equation: (vol. secondary
component)/(vol. first inert material+vol. secondary
component)=0.20 to 1.0.
18. A catalyst bed system for use in adiabatic non-oxidative
dehydrogenation processes comprising: (a) a dehydrogenation
catalyst comprising an active component and a support, wherein said
active component is selected from an oxide of a metal of Group 4 or
Group 5 or Group 6 and combinations thereof, and wherein said
support is selected from aluminum oxide, aluminas, alumina
monohydrate, alumina trihydrate, alumina-silica, transition
aluminas, alpha-alumina, silica, silicate, aluminates, calcined
hydrotalcites, zeolites and combinations thereof; and (b) a first
inert material selected from any material that is catalytically
inactive when subjected to reaction conditions that can effect
dehydrogenation of olefins and that has a high density and high
heat capacity and that is not capable of producing heat during any
stage of the dehydrogenation process; and (c) a secondary component
comprising a heat-generating inert material and a carrier capable
of supporting the heat-generating inert material, wherein said
secondary component is catalytically inert with respect to
dehydrogenation reactions or to cracking or to coking and generates
heat after being exposed to reducing and/or to oxidizing reaction
conditions; and wherein said dehydrogenation catalyst is physically
mixed with said first inert material and then said dehydrogenation
catalyst plus first inert material is physically mixed with said
secondary component.
19. The catalyst bed system of claim 18 wherein said
heat-generating inert material is selected from copper, chromium,
molybdenum, vanadium, cerium, yttrium, scandium, tungsten,
manganese, iron, cobalt, nickel, silver, bismuth and combinations
thereof, and wherein said heat-generating inert material comprises
from about 1 wt % to about 40 wt % of the total secondary component
weight.
20. The catalyst bed system of claim 18 wherein said secondary
component carrier is selected from aluminum oxide, aluminas,
alumina monohydrate, boehmite, pseudo-boehmite, alumina trihydrate,
gibbsite, bayerite, alumina-silica, transition aluminas,
alpha-alumina, silica, silicate, aluminates, calcined
hydrotalcites, zeolites, zinc oxide, chromium oxides, magnesium
oxides and combinations thereof. aterial.
21. The catalyst bed system of claim 18 wherein said secondary
component further comprises a promoter selected from an alkali, an
alkaline earth metal, lithium, sodium, potassium, rubidium, cesium,
beryllium, magnesium, calcium, strontium, barium and a combination
thereof.
22. The catalyst bed system of claim 18 wherein said catalyst and
said first inert material and said secondary component have a
volume relationship defined by the equation: (vol. catalyst)/(vol.
first inert material+vol. secondary component)=0.25 to 0.75. and
wherein said first inert material and said secondary component have
a volume relationship defined by the equation: (vol. secondary
component)/(vol. first inert material+vol. secondary
component)=0.20 to 1.0.
Description
BACKGROUND
[0001] The present development relates to an improved
dehydrogenation catalyst bed system for olefin production utilizing
classical processing techniques. Specifically, the catalyst system
comprises a chromia/alumina dehydrogenation catalyst that further
includes physically mixing the catalyst with at least one other
component that is catalytically inert with respect to
dehydrogenation or side reactions such as cracking or coking but
that generates heat after being exposed to reducing and/or to
oxidizing reaction conditions.
[0002] Dehydrogenation of aliphatic hydrocarbons to produce their
complementary olefins is a well-known process. In the typical
Houdry CATOFIN.RTM. process, an aliphatic hydrocarbon, such as
propane, is passed through a dehydrogenation catalyst bed where the
hydrocarbon is dehydrogenated to its complementary olefin, such as
propylene, the olefin is flushed from the bed, the catalyst is
regenerated and reduced, and the cycle is repeated. (See, for
example, U.S. Pat. No. 2,419,997 and incorporated herein by
reference.)
[0003] The CATOFIN.RTM. dehydrogenation process is an adiabatic,
cyclic process. Each cycle includes a catalyst reduction step, a
dehydrogenation step, a step to purge the remaining hydrocarbon
from the reactor, and finally a regeneration step with air.
Following this, the cycle begins again with the reduction step.
[0004] The dehydrogenation reaction is highly endothermic.
Therefore, during the dehydrogenation step the temperature at the
top of the catalyst bed decreases by as much as 100.degree. C. This
decrease in temperature causes a decrease in paraffin
conversion.
[0005] In order to reheat the catalyst bed and remove coke that has
deposited on the catalyst during the dehydrogenation step, the
reactor is purged of hydrocarbon and then undergoes a regeneration
step with air heated to temperatures of up to 700.degree. C. Heat
is provided to the bed by the hot air that passes through the bed
and also by the combustion of the coke deposits on the catalyst.
Reduction of the catalyst, with a reducing gas such as hydrogen,
prior to dehydrogenation step also provides some additional
heat.
[0006] During regeneration, the hot air flows from the top of the
catalyst bed to the bottom, and the regeneration cycle is
relatively short, so there is a tendency for the top of the bed to
be hotter than the bottom of the bed. The lower temperature in the
bottom of the bed does not allow full utilization of the catalyst
and thus the yield is lower that what would be otherwise expected.
Also, the coke distribution in the catalyst bed, which is not
easily controlled, affects the amount of heat added at each
location and the resulting catalyst bed temperature profile. These
factors make control of the temperature profile in the bed
difficult.
[0007] In the conventional HOUDRY CATOFIN.RTM. process, the reactor
contains a physical mixture of a chromia/alumina catalyst and an
"inert". The volume ratio between the "inert" material and the
catalyst depends on a number of factors including the type of
hydrocarbon feed being used in the dehydrogenation process. For
example, for a propane feed the "inert" material equal to about 50%
of the total catalyst volume, whereas for an isobutane feed the
volume of the "inert" can be as low as about 30% of the total
catalyst bed volume.
[0008] The "inert" is typically a granular, alpha-alumina material
of similar particle size to the catalyst that is catalytically
inactive with respect to dehydrogenation or side reactions such as
cracking or coking, but that has a high density and high heat
capacity, so it can be used to store additional heat in the bed.
The additional heat is then used during the dehydrogenation step.
However, the "inert" is not capable of producing heat during any
stage of the process.
[0009] Since dehydrogenation is a highly endothermic reaction, a
constant challenge related to the Houdry process, and similar
adiabatic non-oxidative dehydrogenation processes, has been to
identify a commercially feasible means for improving the heat
addition to the unit without using a catalytically active material
that produces large quantities of unwanted side products. Thus, it
would be advantageous to identify a catalyst additive that has a
heat capacity and density comparable to the currently used alumina
"inert", and that does not participate to any great extent in the
dehydrogenation reaction or side reactions such as cracking or
coking, and that can be physically mixed with the catalyst before
loading, but that generates heat as needed during the
operation.
SUMMARY OF THE INVENTION
[0010] The present development is a dehydrogenation catalyst bed
system comprising a conventional chromia/alumina dehydrogenation
catalyst that further includes at least one component that is
catalytically inert with respect to dehydrogenation or side
reactions such as cracking or coking but that generates heat after
being exposed to reducing and/or to oxidizing reaction conditions.
In an exemplary embodiment, the heat-generating inert component has
a similar density and heat capacity to alpha-alumina. In a further
exemplary embodiment, the catalyst system comprises a
chromia/alumina catalyst physically mixed with a heat-generating
inert component comprising copper oxide supported on alumina
wherein the copper oxide comprises at least about 8 wt % of the
heat-generating inert component.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0011] The catalyst bed system of the present invention is intended
for use in aliphatic hydrocarbon dehydrogenation reaction
processes, and similar adiabatic non-oxidative dehydrogenation
processes, specifically for the production of olefins. The catalyst
bed system utilized in the process is a chromia/alumina
dehydrogenation catalyst that further comprises a heat-generating
component that is inert with respect to the dehydrogenation
reaction or side reactions such as cracking or coking.
[0012] The equipment used for the dehydrogenation process includes
a reactor bed wherein the bed defines a top section and a bottom
section. In commercial practice, a catalyst is physically mixed
with an inert, such as granular alpha-alumina, and the catalyst
plus inert is then loaded into the reactor bed. An aliphatic
hydrocarbon is fed into the catalyst bed as a gas feed at a
preselected flow rate and such that the feed initially contacts the
top section of the bed and exits after contact with the bottom
section. For the purposes of example herein, the aliphatic
hydrocarbon is propane and the target product is propylene.
[0013] For exemplary purposes only, the process generally follows
the typical "Houdry" process as described in U.S. Pat. No.
2,419,997. The Houdry process includes a series of stages wherein
the catalyst bed is evacuated, reduced with hydrogen and evacuated,
then an aliphatic hydrocarbon is introduced and dehydrogenated,
then the catalyst bed is steam purged and regenerated, and the
cycle is repeated starting with the reduction stage.
[0014] As is known in the art, a catalyst generally has one or more
active components dispersed on or compounded with a carrier or
support. The support provides a means for increasing the surface
area of the catalyst. Several compositions for dehydrogenation
catalysts have been taught in the prior art, such as the catalyst
taught in U.S. Pat. No. 3,488,402 (issued to Michaels et al., and
incorporated herein by reference). The '402 catalyst comprises
"alumina, magnesia, or a combination thereof, promoted with up to
about 40% of an oxide of a metal" of Group 4, Group 5 or Group 6.
(The terms "Group 4", "Group 5" and "Group 6" refer to the new
IUPAC format numbers for the Periodic Table of the Elements.
Alternative terminology, known in the art, includes the old IUPAC
labels "Group IVA," "Group VA" and "Group VI-A", respectively, and
the Chemical Abstract Services version of numbering as "Group IVB,"
"Group VB" and "Group VI-B", respectively.) Recommended carriers
for dehydrogenation catalysts include aluminum oxide, aluminas,
alumina monohydrate, alumina trihydrate, alumina-silica, transition
aluminas, alpha-alumina, silica, silicate, aluminates, calcined
hydrotalcites, zeolites and combinations thereof. For the present
application, the catalyst may be prepared by any standard method
known in the art, such as taught in U.S. Patent Application
20040092391, incorporated herein in its entirety by reference.
[0015] The active dehydrogenation catalyst is then physically mixed
with a first inert material. This first inert material may be any
material that is catalytically inactive with respect to
dehydrogenation or side reactions, such as cracking or coking, and
that has a high density and high heat capacity, but that is not
capable of producing heat during any stage of the process. For the
present application, an exemplary first inert material is a
granular, alpha-alumina material of similar particle size to the
catalyst. As is known in the art, the volume ratio between the
first inert material and the catalyst depends on a number of
factors including the type of hydrocarbon feed being used in the
dehydrogenation process. In the present application, no particular
volume ratio is prescribed, but rather the user may adjust the
ratio as appropriate for the intended use.
[0016] In the present invention, the catalyst and the first inert
material is then further physically combined with at least one
secondary component. The secondary component must be catalytically
inert with respect to dehydrogenation or side reactions such as
cracking or coking but must generate heat after being exposed to
reducing and/or to oxidizing reaction conditions.
[0017] More specifically, the secondary component comprises a
heat-generating inert material and a carrier capable of supporting
the heat-generating inert material. Exemplary carriers for the
secondary component include, but are not limited to, aluminum
oxide, aluminas, alumina monohydrate, boehmite, pseudo-boehmite,
alumina trihydrate, gibbsite, bayerite, alumina-silica, transition
aluminas, alpha-alumina, silica, silicate, aluminates, calcined
hydrotalcites, zeolites, zinc oxide, chromium oxides, magnesium
oxides and combinations thereof.
[0018] The heat-generating inert material may be selected from
copper, chromium, molybdenum, vanadium, cerium, yttrium, scandium,
tungsten, manganese, iron, cobalt, nickel, silver, bismuth and
combinations thereof. The heat-generating inert material comprises
from about 1 wt % to about 40 wt % of the total secondary component
weight. In a more preferred embodiment, the heat-generating inert
material comprises from about 4 wt % to about 20 wt % of the total
secondary component weight; and in a most preferred embodiment, the
amount of heat-generating inert material is from about 6 wt % to
about 10 wt % of the total secondary component weight. Optionally,
the secondary component may further comprise a promoter, such as an
alkali, an alkaline earth metal, lithium, sodium, potassium,
rubidium, cesium, beryllium, magnesium, calcium, strontium, barium
and a combination thereof.
[0019] The secondary component is prepared by essentially the same
methods known in the art for preparing a supported catalyst. For
example, and without limitation, the secondary component may be
prepared by precipitation of the secondary component carrier with
the heat-generating inert material, or by impregnation of the
secondary component carrier with the heat-generating inert
material. Promoters may further be added with the heat-generating
inert material, or may be otherwise added to the secondary
component via methods known in the art for the addition of
promoters. A representative preparation, without limitation, is
alumina trihydrate (gibbsite) is pelletized as approximately 3/16''
pellets, and then the gibbsite is calcined at about 550.degree. C.
for about 4 hours, and the calcined material is then impregnated
with a saturated solution of copper nitrate, and the impregnated
material is dried for about 4 hours at about 250.degree. C. and is
then calcined at from about 500.degree. C. to 1400.degree. C.
[0020] The catalyst bed system is then prepared by physically
mixing or combining the catalyst, the first inert material and the
secondary component. More specifically, the desired amount of
catalyst is defined, and then is mixed with a predetermined amount
of the first inert material and a predetermined amount of the
secondary component. The amount of first inert material is
essentially equal to the amount of inert material that would
normally be combined with the catalyst less the amount of secondary
component to be added. That is, the secondary component is added in
such a manner as to be a complete or partial substitution for the
first inert material. The secondary component does not affect the
amount of catalyst added nor the relative ratio of catalyst to
inert material in the resultant catalyst bed. In an exemplary
embodiment, without limitation, the volume of catalyst used equals
about 25% to about 75% of the volume of the first inert material
plus secondary component or (vol. catalyst)/(vol. first inert
material+vol. secondary component)=0.25 to 0.75. The volume of the
secondary component to be used should be equal to 20 to 100% of the
volume of the first inert material plus secondary component or
(vol. secondary component)/(vol. first inert material+vol.
secondary component)=0.20 to 1.0 The mixture is then loaded into
the reactor in the same manner as traditional dehydrogenation
catalysts are loaded.
[0021] In an improved Houdry process, the catalyst bed is evacuated
and reduced with hydrogen. During this stage, the secondary
component in the reactor bed generates additional heat that passes
into the alumina-supported chromium oxide catalyst portion of the
reactor bed. Then an aliphatic hydrocarbon is fed into the catalyst
bed and is dehydrogenated upon contact with the alumina-supported
chromium oxide catalyst portion of the reactor bed. Because the
alumina-supported chromium oxide catalyst portion of the bed has
been essentially pre-heated by the secondary component, the
alumina-supported chromium oxide catalyst demonstrates improved
conversion relative to a reactor bed that does not include the
secondary component. The catalyst bed is steam purged and
regenerated, and the cycle is repeated starting with the reduction
stage. During the regeneration step, the secondary component may
also generate additional heat. In a preferred embodiment, the
secondary component is selected such that no significant negative
effect on selectivity is observed.
[0022] The catalyst bed system of the present invention is intended
for use in an adiabatic non-oxidative cyclic dehydrogenation
process. The catalyst bed system differs from the catalyst bed
systems of the prior art by requiring that the catalyst comprise a
heat-generating component that is inert with respect to the
dehydrogenation reaction or side reactions such as cracking or
coking. It is understood that the composition of the catalyst and
the specific processing conditions may be varied without exceeding
the scope of this development.
* * * * *